Waste Heat Recovery in Bicycle Manufacturing Process for Specialized Bicycle Components

Abstract

Specialized Bicycle Components, the third largest bicycle brand in the United States, wants to reduce the energy intensity and increase the efficiency of its bicycle manufacturing process. One way to increase efficiency is to reduce or reutilize waste heat. By increasing the efficiency of the manufacturing process, the company hopes to save money and set an example for the rest of the industry to make a commitment towards more environmentally conscious manufacturing. The main problem to be addressed in this report is how to feasibly and economically reduce or reuse waste heat. To determine if Specialized can reduce or reuse waste heat, our Duke team has calculated heat inputs and outputs of the heat treatment process, completed an exhaustive literature review of waste heat recovery technologies, and performed cost-benefit analyses of potential solutions. We also present our recommendations on how Specialized can most effectively reduce waste heat and increase overall efficiency. The first section of this report provides a technical description and visual representation of the bicycle manufacturing process. The description explains the two necessary heat treatments for manufacturing bicycle frames, tempering and aging, and the different heat flows in and out of the oven. The data used in this description is specific to Specialized’s industrial oven in Taiwan. The second section of the report quantifies the heat treatment processes with thermodynamic calculations. Using data from Specialized's manufacturing facility, the heat inputs and outputs of the current heat treatment oven were calculated. It was found that the heat treatment process requires 507.53 MWh per year, which costs $24,921.58 per year. Of this total energy requirement, 451.60 MWh is lost as waste heat – energy that is not performing useful work. This waste heat costs the company $22,174.97 per year. Because the company is losing a substantial amount of money through waste heat, it is worth considering methods and technologies that can help reduce or recycle this waste heat. If Specialized is able to reduce or recycle waste heat, they can save thousands of dollars each year and reduce facility emissions significantly. The third section of this report examines waste heat recovery methods and technologies that are suitable for bicycle manufacturing processes. The purpose of waste heat recovery technologies is to make use of this secondary source of energy, recognizing that utilizing the rejected or waste heat can substantially improve system efficiencies. To examine the waste heat recovery methods and technologies, a comprehensive literature review was completed. This research, based in both academic and industrial sectors, allowed us to evaluate the performance of the proposed technologies and examine how they could be added onto the existing manufacturing process. Cost-benefit analyses were also presented to determine whether the potential waste heat recovery solutions were feasible and economical for Specialized to implement. If they were not feasible and economical, they were rejected. The fourth section of this report provides two recommendations to Specialized for feasibly and economically reducing waste heat. After literature review and cost-benefit analyses, it was concluded that Specialized could not implement commonly used waste heat recovery technologies, such as air fans, vestibules, or heat exchanges, because they were not feasible or economical. The waste heat the manufacturing process generates is not large or hot enough to reuse in an efficient way. Therefore, the recommendations focused on reducing waste heat rather than reutilizing. The recommendations include instructions on how Specialized could implement the recommended changes into their current manufacturing setting, and how much energy and money the company could save through implementation. The first recommendation is to switch the industrial oven’s fuel source from liquified petroleum gas (LPG) to natural gas. Fuel switching can save more than $600 per month and reduce emissions by 15%. Additionally, it requires minimal implementation costs because LPG equipment can easily be converted for natural gas use. The second recommendation is to replace the frame holders from steel to carbon-carbon composite. The frame holders absorb a substantial amount of heat input, which is lost to waste heat. Carbon-carbon composite absorbs less heat input during the process because of the material’s lower mass compared to steel. Although there is a considerable investment cost associated with this recommendation, the materials change is prudent because the payback period is relatively short; it only takes 17 months until the company can recover its investments costs.